U.S. patent application number 12/498456 was filed with the patent office on 2010-01-14 for filter with disk-shaped electrode pattern.
This patent application is currently assigned to FUJITSU LIMITED. Invention is credited to Akihiko Akasegawa, Kazuaki Kurihara, Teru Nakanishi, Keisuke Sato, Kazunori Yamanaka.
Application Number | 20100009854 12/498456 |
Document ID | / |
Family ID | 41505686 |
Filed Date | 2010-01-14 |
United States Patent
Application |
20100009854 |
Kind Code |
A1 |
Sato; Keisuke ; et
al. |
January 14, 2010 |
FILTER WITH DISK-SHAPED ELECTRODE PATTERN
Abstract
A filter includes a dielectric substrate; an electrode layer
continuously formed covering a first side of the dielectric
substrate; a disk-shaped electrode pattern provided on a second
side of the dielectric substrate, the disk-shaped electrode pattern
and the electrode layer holding the dielectric substrate
therebetween; a ground slot having an opening that is formed
asymmetrically with respect to the center of a circular area
included in the electrode layer and exposes the dielectric
substrate, the circular area and the disk-shaped electrode pattern
holding the dielectric substrate therebetween.
Inventors: |
Sato; Keisuke; (Kawasaki,
JP) ; Nakanishi; Teru; (Kawasaki, JP) ;
Akasegawa; Akihiko; (Kawasaki, JP) ; Yamanaka;
Kazunori; (Kawasaki, JP) ; Kurihara; Kazuaki;
(Kawasaki, JP) |
Correspondence
Address: |
WESTERMAN, HATTORI, DANIELS & ADRIAN, LLP
1250 CONNECTICUT AVENUE, NW, SUITE 700
WASHINGTON
DC
20036
US
|
Assignee: |
FUJITSU LIMITED
Kawasaki-shi
JP
|
Family ID: |
41505686 |
Appl. No.: |
12/498456 |
Filed: |
July 7, 2009 |
Current U.S.
Class: |
505/210 |
Current CPC
Class: |
H01P 1/20381 20130101;
H01B 12/02 20130101; H01P 1/203 20130101 |
Class at
Publication: |
505/210 |
International
Class: |
H01P 1/203 20060101
H01P001/203; H01L 39/02 20060101 H01L039/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 8, 2008 |
JP |
2008-178100 |
Claims
1. A filter comprising: a dielectric substrate; an electrode layer
continuously formed covering a first side of the dielectric
substrate; a disk-shaped electrode pattern provided on a second
side of the dielectric substrate, the disk-shaped electrode pattern
and the electrode layer holding the dielectric substrate
therebetween; a ground slot having an opening that is formed
asymmetrically with respect to the center of a circular area
included in the electrode layer and exposes the dielectric
substrate, the circular area, and the disk-shaped electrode pattern
holding the dielectric substrate therebetween; an input-side cutout
portion that is formed in the electrode layer on the first side of
the dielectric substrate so as to reach the circular area and
extends in a first direction; an output-side cutout portion that is
formed in the electrode layer on the first side of the dielectric
substrate so as to reach the circular area and extends in a second
direction perpendicular to the first direction; an input-side
conductive pattern formed in the input-side cutout portion on the
first side of the dielectric substrate; and an output-side
conductive pattern formed in the output-side cutout portion on the
first side of the dielectric substrate.
2. The filter according to claim 1, wherein the input-side
conductive pattern has a form that corresponds to a form of the
input-side cutout portion, and the output-side conductive pattern
has a form that corresponds to a form of the output-side cutout
portion.
3. The filter according to claim 2, wherein the input-side cutout
portion and the input-side conductive pattern form a first
coplanar-type feeder line, and the output-side cutout portion and
the output-side conductive pattern form a second coplanar-type
feeder line.
4. The filter according to claim 1, wherein the ground slot has a
circular opening.
5. The filter according to claim 1, further comprising: an
adjustment rod adjacent to the first side of the dielectric
substrate, the adjustment rod being opposite the ground slot and
being composed of a magnetic or dielectric material.
6. The filter according to claim 5, wherein the adjustment rod is
held in such a manner that the adjustment rod is adjustable to be
closer to or further away from the ground slot.
7. The filter according to claim 1, wherein the electrode layer,
the electrode pattern, the input-side conductive pattern, and the
output-side conductive pattern are composed of a
superconductor.
8. A filter comprising: a dielectric substrate including a first
area and a second area; a first electrode pattern formed in the
first area on a first side of the dielectric substrate; a second
electrode pattern formed in the second area on the first side of
the dielectric substrate; a connection electrode pattern that
connects the first and second electrode patterns and extends over
the first side of the dielectric substrate; a disk-shaped third
electrode pattern provided on a second side of the dielectric
substrate that is opposite the first side thereof, the disk-shaped
third electrode pattern and the first electrode pattern holding the
dielectric substrate therebetween in the first area; a disk-shaped
fourth electrode pattern provided on the second side of the
dielectric substrate, the disk-shaped fourth electrode pattern and
the second electrode pattern holding the dielectric substrate
therebetween in the second area; an input-side cutout portion that
is formed in the first electrode pattern on the first side of the
dielectric substrate so as to reach the first area and extends in a
direction perpendicular to the direction in which the connection
electrode pattern extends; an output-side cutout portion that is
formed, parallel to the input-side cutout portion, in the second
electrode pattern on the first side of the dielectric substrate so
as to reach the second area; an input-side conductive pattern that
is formed in the input-side cutout portion on the first side of the
dielectric substrate, the input-side conductive pattern and the
first electrode pattern forming a first signal transmission line;
an output-side conductive pattern that is formed in the output-side
cutout portion on the first side of the dielectric substrate, the
output-side conductive pattern and the second electrode pattern
forming a second signal transmission line; a first ground slot that
includes a first opening formed asymmetrically in a first circular
area included in the first electrode pattern with respect to the
center of the first circular area, the first opening exposing the
dielectric substrate, the first circular area, and the disk-shaped
third electrode pattern holding the dielectric substrate
therebetween; and a second ground slot that includes a second
opening formed asymmetrically in a second circular area included in
the second electrode pattern with respect to the center of the
second circular area, the second opening exposing the dielectric
substrate, the second circular area, and the disk-shaped fourth
electrode pattern holding the dielectric substrate
therebetween.
9. The filter according to claim 8, wherein the input-side cutout
portion and the input-side conductive pattern form a first
coplanar-type feeder line, and the output-side cutout portion and
the output-side conductive pattern form a second coplanar-type
feeder line.
10. The filter according to claim 8, further comprising: a third
ground slot including a third opening formed in the connection
electrode pattern, the third opening exposing the dielectric
substrate.
11. The filter according to claim 10, wherein a first adjustment
rod, a second adjustment rod, and a third adjustment rod, each
composed of a magnetic or dielectric material, are provided in the
first ground slot, the second ground slot, and the third ground
slot respectively, in such a manner that the positions of the
first, second, and third adjustment rods are adjustable to be
closer to or further away from the first, second, and third ground
slots, respectively.
12. The filter according to claim 8, wherein the first and second
electrode patterns, the disk-shaped third and fourth electrode
patterns, the connection electrode pattern, the input-side
conductive pattern, and the output-side conductive pattern are
composed of a superconductor.
13. A filter comprising: a dielectric substrate including a first
area and a second area; a first electrode pattern formed in the
first area on the first side of the dielectric substrate; a second
electrode pattern formed in the second area on the first side of
the dielectric substrate; a connection electrode pattern that
connects the first and second electrode patterns and extends over
the first side of the dielectric substrate; a disk-shaped third
electrode pattern provided on a second side of the dielectric
substrate that is opposite the first side thereof, the disk-shaped
third electrode pattern and the first electrode pattern holding the
dielectric substrate therebetween in the first area; a disk-shaped
fourth electrode pattern provided on the second side of the
dielectric substrate, the disk-shaped fourth electrode pattern and
the second electrode pattern holding the dielectric substrate
therebetween in the second area; an input-side cutout portion that
is formed in the first electrode pattern on the first side of the
dielectric substrate so as to reach the first area and extends in a
direction parallel to the direction in which the connection
electrode pattern extends; an output-side cutout portion that is
formed, parallel to the input-side cutout portion, in the second
electrode pattern on the first side of the dielectric substrate so
as to reach the second area; an input-side conductive pattern that
is formed in the input-side cutout portion on the first side of the
dielectric substrate, the input-side conductive pattern and the
first electrode pattern forming a first signal transmission line;
and an output-side conductive pattern that is formed in the
output-side cutout portion on the first side of the dielectric
substrate, the output-side conductive pattern and the second
electrode pattern forming a second signal transmission line.
14. The filter according to claim 13, wherein the input-side cutout
portion and the input-side conductive pattern form a first
coplanar-type feeder line, and the output-side cutout portion and
the output-side conductive pattern form a second coplanar-type
feeder line.
15. The filter according to claim 13, further comprising: an
adjustment rod composed of a magnetic or dielectric material in
such a manner that the adjustment rod is opposite the ground slot
and adjustable to be closer thereto or further away therefrom, the
adjustment rod corresponding to the center of a virtual line
connecting the centers of the disk-shaped third and fourth
electrode patterns in the connection electrode pattern.
16. The filter according to claim 13, wherein the first and second
electrode patterns, the disk-shaped third and fourth electrode
pattern, the connection electrode pattern, the input-side
conductive pattern, and the output-side conductive pattern are
composed of a superconductor.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority of the prior Japanese Patent Application No. 2008-178100,
filed on Jul. 8, 2008 the entire contents of which are incorporated
herein by reference.
FIELD
[0002] The present invention relates to filters, and more
particularly to a filter that has a disk-shaped electrode
pattern.
BACKGROUND
[0003] Filters that include a microstrip line using a
superconducting film are low-loss filters and are expected to be
applied to GHz-band high-power transmission apparatuses such as
base stations for mobile communication.
[0004] However, the superconductivity of a superconducting film
tends to deteriorate when power applied to the superconducting film
is high; thus it has been difficult to apply such a superconducting
film in high-power applications.
[0005] For this problem, a filter that uses a disk-shaped electrode
pattern and prevents power to be applied to the filter from being
high has been proposed.
[0006] Moreover, in order to obtain a steep filter characteristic,
a technology has been proposed in which a multiple-stage filter is
configured by arranging a plurality of resonators, each of which is
provided with a disk-shaped electrode pattern, on a dielectric
substrate and by coupling the resonators.
[0007] FIG. 1 presents a schematic structure of a superconducting
tunable filter 10 disclosed in Japanese Laid-open Patent
Publication No. 2008-28835.
[0008] Referring to FIG. 1, the superconducting tunable filter 10
is formed on a dielectric substrate 11. The superconducting tunable
filter 10 includes a superconducting ground layer 12 that covers
the back-side surface of the dielectric substrate 11,
superconducting disk-shaped electrode patterns 13A, 13B, 13C, and
13D that are formed on the front-side surface of the dielectric
substrate 11, a superconducting input-side feeder pattern 14A that
is coupled to the superconducting disk-shaped electrode pattern
13A, a superconducting output-side feeder pattern 14E that is
coupled to the superconducting disk-shaped electrode pattern 13D, a
superconducting feeder pattern 14B that is used to couple the
superconducting disk-shaped electrode pattern 13A to the
superconducting disk-shaped electrode pattern 13B, a
superconducting feeder pattern 14C that is used to couple the
superconducting disk-shaped electrode pattern 13B to the
superconducting disk-shaped electrode pattern 13C, and a
superconducting feeder pattern 14D that is used to couple the
superconducting disk-shaped electrode pattern 13C to the
superconducting disk-shaped electrode pattern 13D. A dielectric
plate 15 is provided apart from the front-side surface of the
dielectric substrate 11 in such a manner that the dielectric plate
15 may be adjusted to be closer to or further away from the
front-side surface of the dielectric substrate 11. The dielectric
plate 15 enables adjustment of the center frequency of the
superconducting tunable filter 10.
[0009] In the superconducting tunable filter 10 configured like
this, the superconducting disk-shaped electrode patterns 13A to 13D
prevent the intensity of an electric field from being high. Thus,
the superconducting tunable filter 10 may be applied to high-power
applications.
[0010] Moreover, holes 15A to 15E to that allow adjustment rods
composed of a dielectric or magnetic material to pass therethrough
are formed in the dielectric plate 15. Although not presented,
adjustment rods composed of a magnetic or dielectric material are
formed in such a manner that the adjustment rods may be adjusted to
be closer to or further away from the superconducting disk-shaped
electrode patterns 13A to 13D and the superconducting feeder
patterns 14B and 14D through the holes 15A to 15E. With this
structure, the bandwidth of the superconducting tunable filter 10
may be adjusted using the adjustment rods.
[0011] In the superconducting tunable filter 10 presented in FIG.
1, which is a related art superconducting tunable filter, the
dielectric plate 15 is coupled not only to the superconducting
disk-shaped electrode patterns 13A to 13D but also to the
superconducting input-side and output-side feeder patterns 14A and
14E and the superconducting feeder patterns 14B to 14D. Thus, if
the center frequency of the superconducting tunable filter 10 is
adjusted by moving the dielectric plate 15 closer to or further
away from the front-side surface of the dielectric substrate 11,
coupling states of the superconducting input-side and output-side
feeder patterns 14A and 14E and the superconducting feeder patterns
14B to 14D and the superconducting disk-shaped electrode patterns
13A to 13D also change. As a result, for the superconducting
tunable filter 10 presented in FIG. 1, there is a problem in that
adjustment of filter characteristics such as the center frequency
and the bandwidth becomes complicated. Moreover, in the
superconducting tunable filter 10 disclosed in FIG. 1, for example,
the superconducting input-side and output-side feeder patterns 14A
and 14E are coupled to curved peripheries of the superconducting
disk-shaped electrode patterns 13A and 13D, respectively, from the
outside. Thus, the area of a connecting portion, that is, the
capacitance of the connecting portion is small, and it is difficult
to ensure an appropriate connection. The same problem exists for
the superconducting feeder patterns 14B to 14D. Thus, for the
superconducting tunable filter 10 disclosed in FIG. 1,
significantly suppressing loss is difficult.
SUMMARY
[0012] According to one aspect of the invention, a filter includes
a dielectric substrate; an electrode layer continuously formed
covering a first side of the dielectric substrate; a disk-shaped
electrode pattern provided on a second side of the dielectric
substrate, the disk-shaped electrode pattern, and the electrode
layer holding the dielectric substrate therebetween; a ground slot
having an opening that is formed asymmetrically with respect to the
center of a circular area included in the electrode layer and
exposes the dielectric substrate, the circular area, and the
disk-shaped electrode pattern holding the dielectric substrate
therebetween.
[0013] The object and advantages of the invention will be realized
and attained by means of the elements and combinations particularly
pointed out in the claims.
[0014] It is to be understood that both the foregoing general
description and the following detailed description are exemplary
and explanatory and are not restrictive of the invention, as
claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a diagram of a related art superconducting
filter.
[0016] FIG. 2A is a plan view of a superconducting resonator
according to a first embodiment.
[0017] FIG. 2B is a bottom view of the superconducting resonator
according to the first embodiment.
[0018] FIG. 2C is a sectional view of the superconducting resonator
according to the first embodiment, the sectional view being taken
along line A-A' in FIG. 2B.
[0019] FIG. 3 is a diagram illustrating a reflection characteristic
of the superconducting resonator illustrated in FIGS. 2A to 2C.
[0020] FIG. 4 is a diagram of an inter-mode coupling coefficient of
the superconducting resonator illustrated in FIGS. 2A to 2C.
[0021] FIG. 5 is a sectional view of a superconducting filter
according to a second embodiment.
[0022] FIG. 6 is a diagram of a transmission characteristic of the
superconducting filter illustrated in FIG. 5.
[0023] FIG. 7 is a sectional view of a superconducting filter
according to a third embodiment.
[0024] FIG. 8 is a diagram of a reflection characteristic of the
superconducting filter illustrated in FIG. 7.
[0025] FIG. 9 is a diagram of a reflection characteristic of the
superconducting filter illustrated in FIG. 7.
[0026] FIG. 10 is a diagram of an inter-mode coupling coefficient
of the superconducting filter illustrated in FIG. 7.
[0027] FIG. 11A is a plan view of a superconducting resonator
according to a fourth embodiment.
[0028] FIG. 11B is a bottom view of the superconducting resonator
according to the fourth embodiment.
[0029] FIG. 11C is a sectional view of the superconducting
resonator according to the fourth embodiment, the sectional view
being taken along line B-B' in FIG. 11B.
[0030] FIG. 12 is a diagram of a reflection characteristic of the
superconducting resonator illustrated in FIGS. 11A to 11C.
[0031] FIG. 13 is a diagram of an inter-resonator coupling
coefficient of the superconducting resonator illustrated in FIGS.
11A to 11C.
[0032] FIG. 14 is a sectional view of a superconducting filter
according to a fifth embodiment.
[0033] FIG. 15A is a plan view of a superconducting resonator used
in the superconducting filter illustrated in FIG. 14.
[0034] FIG. 15B is a bottom view of the superconducting resonator
used in the superconducting filter illustrated in FIG. 14.
[0035] FIG. 15C is a sectional view of the superconducting
resonator used in the superconducting filter illustrated in FIG.
14, the sectional view being taken along line C-C' in FIG. 15B.
[0036] FIG. 16 is a diagram of a reflection characteristic of the
superconducting filter illustrated in FIG. 14.
[0037] FIG. 17 is a diagram of a transmission characteristic of the
superconducting filter illustrated in FIG. 14.
[0038] FIG. 18 is a diagram of an inter-resonator coupling
coefficient of the superconducting filter illustrated in FIG.
14.
[0039] FIG. 19A is a plan view of a superconducting resonator
according to a sixth embodiment.
[0040] FIG. 19B is a bottom view of the superconducting resonator
according to the sixth embodiment.
[0041] FIG. 19C is a sectional view of the superconducting
resonator according to the sixth embodiment, the sectional view
being taken along line D-D' in FIG. 19B.
[0042] FIG. 20 is a diagram of a reflection characteristic of the
superconducting filter illustrated in FIGS. 19A to 19C.
[0043] FIG. 21 is a sectional view of a superconducting filter
according to a seventh embodiment.
[0044] FIG. 22A is a plan view of a superconducting resonator used
in the superconducting filter illustrated in FIG. 21.
[0045] FIG. 22B is a bottom view of the superconducting resonator
used in the superconducting filter illustrated in FIG. 21.
[0046] FIG. 22C is a sectional view of the superconducting
resonator used in the superconducting filter illustrated in FIG.
21, the sectional view being taken along line E-E' in FIG. 22B.
[0047] FIG. 23 is a block diagram of a transmitter-receiver
according to an eighth embodiment.
DESCRIPTION OF EMBODIMENTS
First Embodiment
[0048] FIGS. 2A to 2C are a plan view, a bottom view, and a
sectional view taken along line A-A' in FIG. 2B, respectively, of a
structure of a superconducting dual-mode resonator 20 according to
a first embodiment.
[0049] Referring to FIGS. 2A to 2C, the superconducting dual-mode
resonator 20 is formed on a low-loss dielectric substrate 21 having
a thickness of, for example, 0.5 mm and composed of MgO or the
like. An electrode layer 22 having a thickness of, for example, 0.5
.mu.m and composed of, for example, a YBCO (Y--Ba--Cu--O)
high-temperature superconductor is uniformly formed on the bottom
surface of the low-loss dielectric substrate 21. Moreover, a
disk-shaped electrode pattern 23 composed of the same
high-temperature superconductor as described above and having, for
example, a thickness of 0.5 .mu.m and a radius of 5.6 mm is formed
on the top surface of the low-loss dielectric substrate 21.
[0050] A circular opening 22B having, for example, a radius of 1 mm
is formed in the electrode layer 22 at a position away from the
center of a circular area 22A in such a manner that the circular
opening 22B exposes the bottom surface of the low-loss dielectric
substrate 21. The circular area 22A and the disk-shaped electrode
pattern 23 hold the low-loss dielectric substrate 21 therebetween.
Furthermore, a first feeder cutout portion 22a is formed in the
electrode layer 22 in such a manner that the first feeder cutout
portion 22a reaches the circular area 22A from part of the
periphery of the low-loss dielectric substrate 21 and exposes the
bottom surface of the low-loss dielectric substrate 21. Moreover, a
second feeder cutout portion 22b is formed in the electrode layer
22 in such a manner that the second feeder cutout portion 22b
reaches the circular area 22A from part of the periphery of the
low-loss dielectric substrate 21. The second feeder cutout portion
22b also exposes the bottom surface of the low-loss dielectric
substrate 21, and is formed perpendicular to the first feeder
cutout portion 22a.
[0051] Furthermore, an input-side conductive pattern 22c composed
of the same superconductor as described above is formed in the
first feeder cutout portion 22a, and the first feeder cutout
portion 22a and the input-side conductive pattern 22c form an
input-side coplanar-type feeder line (hereinafter referred to as an
"input-side feeder line"). Similarly, an output-side conductive
pattern 22d composed of the same superconductor as described above
is formed in the second feeder cutout portion 22b. Similarly, the
second feeder cutout portion 22b and the output-side conductive
pattern 22d form an output-side coplanar-type feeder line
(hereinafter referred to as an "output-side feeder line").
[0052] An electric field component of an input signal supplied from
the input-side conductive pattern 22c vibrates in the direction
indicated by Mode 1 in FIG. 2A in the superconducting dual-mode
resonator 20. In contrast, an electric field component of an output
signal output to the output-side conductive pattern 22d vibrates in
the direction indicated by Mode 2 in FIG. 2A in the superconducting
dual-mode resonator 20. A ground slot 22B formed in the electrode
layer 22 functions so as to couple these two modes together.
[0053] FIG. 3 illustrates reflection characteristics (S.sub.11
parameters) obtained at a temperature of 70 K of the
superconducting dual-mode resonator 20 illustrated in FIGS. 2A to
2C. As is well known in the art, the S.sub.11 parameter indicates a
reflection characteristic of a filter from the viewpoint of the
input side. Here, FIG. 3 illustrates cases where the radii of the
ground slot 22B are 1.0 mm, 1.2 mm, 1.3 mm, and 1.4 mm.
[0054] Referring to FIG. 3, peaks having resonance frequencies
f.sub.1, and f.sub.2 appear in the reflection characteristic graph
at the low-frequency side and at the high-frequency side,
respectively. FIG. 3 illustrates that the gap between the resonance
frequencies f.sub.1 and f.sub.2 increases as the radius of the
ground slot 22B increases. This indicates that the degree of
coupling between the modes performed by the ground slot 22B
increases as the radius of the ground slot 22B increases.
[0055] FIG. 4 illustrates a relationship between a coupling
coefficient k.sub.slot used for coupling the modes (hereinafter
referred to as an inter-mode coupling coefficient k.sub.slot) and
the radius of the ground slot 22B, the coupling coefficient
k.sub.slot being obtained from the reflection characteristic in
FIG. 3. Here, the inter-mode coupling coefficient k.sub.slot is
expressed by the expression
k.sub.slot=(f.sub.22-f.sub.12)/(f.sub.22+f.sub.12)(f.sub.2>f.sub.1).
[0056] Referring to FIG. 4, the relationship established between
the radius of the ground slot 22B and the inter-mode coupling
coefficient k.sub.slot is almost linear. Here, a case where the
radius of the slot illustrated in FIG. 4 is 1.1 mm is not depicted
in FIG. 3 in order to prevent FIG. 3 from becoming complicated.
[0057] In the first embodiment, the input-side feeder line
including the first feeder cutout portion 22a and the input-side
conductive pattern 22c and the output-side feeder line including
the second feeder cutout portion 22b and the output-side conductive
pattern 22d are formed in such a manner that they reach the
circular area 22A within the electrode layer 22 continuously formed
on the back-side surface of the low-loss dielectric substrate 21.
As a result, according to the present invention, strong coupling
may be achieved between the input-side conductive pattern 22c and
the electrode layer 22 and between the output-side conductive
pattern 22d and the electrode layer 22. That is, according to the
first embodiment, loss caused by using the superconducting
dual-mode resonator 20 or loss caused by using a filter using the
superconducting dual-mode resonator 20 may be more significantly
reduced than when feeder lines are formed on the front-side surface
of the low-loss dielectric substrate 21.
[0058] Here, in the first embodiment, the low-loss dielectric
substrate 21 is not limited to an MgO single crystal substrate and
may alternatively be a LaAIO.sub.3 single crystal substrate or a
sapphire substrate.
[0059] Furthermore, the electrode layer 22, the disk-shaped
electrode pattern 23, and the input-side and output-side conductive
patterns 22c and 22d are not limited to those composed of the YBCO
high-temperature superconductor and may alternatively be composed
of, for example, an R--Ba--Cu--O (RBCO) high-temperature
superconductor film, that is, a film composed of neodymium (Nd),
samarium (Sm), gadolinium (Gd), dysprosium (Dy), or holmium (Ho)
instead of yttrium (Y) in the YBCO high-temperature
superconductor.
[0060] Furthermore, Ba--Sr--Ca--Cu--O (BSCCO),
Pb--Bi--Sr--Ca--Cu--O (PBSCCO), and
Cu--Ba.sub.p--Ca.sub.q--Cu.sub.r-Ox (CBCCO) (where 1.5<p<2.5,
2.5<q<3.5, 3.5<r<4.5) high-temperature superconductors
may alternatively be used in the first embodiment.
[0061] In the first embodiment, the intensity of an electric field
may be prevented from becoming high and the problem of the
electrode layer 22 losing its superconductivity because of an
intense electric field may be reduced if not prevented from
occurring by forming the ground slot 22B in a circular shape.
[0062] Here, in the superconducting dual-mode resonator 20
according to the first embodiment, the electrode layer 22, the
disk-shaped electrode pattern 23, the input-side conductive pattern
22c, and the output-side conductive pattern 22d are not necessarily
composed of a high-temperature superconductor, and may
alternatively be composed of a normal conductor.
[0063] The superconducting dual-mode resonator 20 according to the
first embodiment may be used as a GHz-band filter.
Second Embodiment
[0064] FIG. 5 illustrates a superconducting filter 30 according to
a second embodiment using the superconducting dual-mode resonator
20.
[0065] Referring to FIG. 5, the superconducting filter 30 includes
a package container 31 that carries a wiring pattern (not shown)
formed as a microstrip line on the bottom portion of the
superconducting filter 30. The superconducting dual-mode resonator
20 may be mounted on the bottom portion of the package container 31
by a flip-chip method. Moreover, an opening 31B corresponding to
the ground slot 22B is formed in the bottom portion of the package
container 31.
[0066] Furthermore, a dielectric plate 32 composed of MgO,
sapphire, or the like is arranged above the superconducting
dual-mode resonator 20 in the package container 31. The dielectric
plate 32 is held by a cover 31L of the package container 31 using
screws 32A and 32B and the like in such a manner that the
dielectric plate 32 may be adjusted to be closer to or further away
from the superconducting dual-mode resonator 20. The distance
between the dielectric plate 32 and the superconducting dual-mode
resonator 20 may be adjusted to be in the range of 0.01 mm to 10
mm.
[0067] FIG. 6 illustrates a transmission characteristic of the
superconducting filter 30, the transmission characteristic being
obtained at a temperature of 60 K.
[0068] Referring to FIG. 6, the transmission characteristic
corresponds to the reflection characteristic in FIG. 3. FIG. 6
shows that the passband width of the superconducting filter 30 may
be freely set by setting the size of the ground slot 22B, without
the center frequency of the superconducting filter 30 being
substantially changed.
[0069] Furthermore, in the superconducting filter 30 illustrated in
FIG. 5, the center frequency of the superconducting filter 30 may
be changed by adjusting the distance between the superconducting
dual-mode resonator 20 and the dielectric plate 32 using the screws
32A and 32B, without the passband width illustrated in the
transmission characteristic in FIG. 6 being substantially changed.
The center frequency of the superconducting filter 30 increases as
the dielectric plate 32 is adjusted to be closer to the
superconducting dual-mode resonator 20, and the center frequency
thereof decreases as the dielectric plate 32 is adjusted to be
further away from the superconducting dual-mode resonator 20.
[0070] The dielectric plate 32 and the screws 32A and 32B may be
omitted in the superconducting filter 30 in FIG. 5.
[0071] In the second embodiment, as described above, the input-side
feeder line including the first feeder cutout portion 22a and the
input-side conductive pattern 22c and the output-side feeder line
including the second feeder cutout portion 22b and the output-side
conductive pattern 22d are formed in such a manner that they reach
the circular area 22A within the electrode layer 22 continuously
formed on the back-side surface of the low-loss dielectric
substrate 21. As a result, according to the present invention,
strong coupling may be achieved between the input-side conductive
pattern 22c and the electrode layer 22 and between the output-side
conductive pattern 22d and the electrode layer 22. That is,
according to the second embodiment, loss caused by using the
superconducting dual-mode resonator 20 or loss caused by using a
filter using the superconducting dual-mode resonator 20 may be more
significantly reduced than the case in which feeder lines are
formed on the front-side surface of the low-loss dielectric
substrate 21.
Third Embodiment
[0072] FIG. 7 illustrates a superconducting filter 40 according to
a third embodiment.
[0073] Referring to FIG. 7, the superconducting filter 40 includes
a package container 41 that carries a wiring pattern (not shown)
formed as a microstrip line on the bottom portion of the
superconducting filter 40, and the superconducting dual-mode
resonator 20 is mounted on the bottom portion of the package
container 41 by a flip-chip method. Moreover, an opening 41B
corresponding to the ground slot 22B is formed in the bottom
portion of the package container 41.
[0074] Furthermore, a dielectric plate 42 composed of MgO,
sapphire, or the like is arranged above the superconducting
dual-mode resonator 20 in the package container 41. The dielectric
plate 42 is held by a cover 41L of the package container 41 using
screws 42A and 42B and the like in such a manner that the
dielectric plate 42 may be adjusted to be closer to or further away
from the superconducting dual-mode resonator 20. The distance
between the dielectric plate 42 and the superconducting dual-mode
resonator 20 may be adjusted to be in the range of 0.01 mm to 10
mm.
[0075] Furthermore, a rod 41C corresponding to the ground slot 22B
and having a screw shape is formed in the opening 41B of the
superconducting filter 40 in such a manner that the rod 41C may be
adjusted to be closer to or further away from the low-loss
dielectric substrate 21. The distance h.sub.slot between the rod
41C and the low-loss dielectric substrate 21 may be adjusted to be
in the range of 0.01 mm to 1 mm.
[0076] As described above using FIGS. 3 and 4, the passband width
of the superconducting dual-mode resonator 20 is controlled by the
radius of the ground slot 22B, and the inter-mode coupling
coefficient k.sub.slot in the superconducting dual-mode resonator
20 is controlled by the radius of the ground slot 22B.
[0077] Thus, in the third embodiment, the inter-mode coupling
coefficient k.sub.slot may be controlled by adjusting the rod 41C
to be closer to or further away from the ground slot 22B, whereby
the passband characteristic of the superconducting filter 40 is
controlled.
[0078] FIG. 8 illustrates a reflection characteristic (S11) of the
superconducting filter 40 at a temperature of 60 K, and FIG. 9
illustrates a passband characteristic of the superconducting filter
40 in cases where h.sub.slot=0.02 mm, h.sub.slot=0.07 mm,
h.sub.slot=0.12 mm, and h.sub.slot=0.42 mm. In an example in FIG.
8, a metal screw having a radius of 2 mm is used as the rod 41C.
The rod 41C may be composed of a magnetic material or a dielectric
material such as MgO, LaAIO.sub.3, TiO.sub.2, or the like.
[0079] As may be seen from FIGS. 8 and 9, the passband width of the
superconducting filter 40 decreases as the distance h.sub.slot
becomes smaller and increases as the distance h.sub.slot becomes
larger. Moreover, FIGS. 8 and 9 illustrate that if the distance
h.sub.slot is changed by the rod 41C, the center frequency of the
superconducting filter 40 changes. If the distance h.sub.slot
decreases, the center frequency of the superconducting filter 40 is
shifted and becomes lower. If the distance h.sub.slot increases,
the center frequency of the superconducting filter 40 is shifted
and becomes higher. However, such a shift regarding the center
frequency of the superconducting filter 40 may be compensated by
changing the distance between the dielectric plate 42 and the
superconducting dual-mode resonator 20 using the screws 42A and
42B.
[0080] FIG. 10 illustrates a relationship between the inter-mode
coupling coefficient k.sub.slot and the distance h.sub.slot for the
superconducting filter 40. The inter-mode coupling coefficient
k.sub.slot is obtained at a temperature of 70 K from the reflection
characteristic in FIG. 8.
[0081] Referring to FIG. 10, as the distance h.sub.slot decreases,
the inter-mode coupling coefficient k.sub.slot decreases, and the
characteristics of the superconducting filter 40 become similar to
those of a single-mode filter. As a result, the passband width
decreases. In contrast, as the distance h.sub.slot increases, the
effect of the ground slot 22B increases, whereby the
characteristics of the superconducting filter 40 become similar
than those of a dual-mode filter. As a result, the passband width
increases as illustrated in FIGS. 8 and 9.
[0082] The dielectric plate 42 and the screws 42A and 42B may be
omitted in the superconducting filter 40 illustrated in FIG. 7.
[0083] In the third embodiment, as described above, the input-side
feeder line including the first feeder cutout portion 22a and the
input-side conductive pattern 22c and the output-side feeder line
including the second feeder cutout portion 22b and the output-side
conductive pattern 22d are formed in such a manner that they reach
the circular area 22A within the electrode layer 22 continuously
formed on the back-side surface of the low-loss dielectric
substrate 21. As a result, according to the present invention,
strong coupling may be achieved between the input-side conductive
pattern 22c and the electrode layer 22 and between the output-side
conductive pattern 22d and the electrode layer 22. That is,
according to the third embodiment, loss caused by using the
superconducting filter 40 may be more significantly reduced than
the case in which feeder lines are formed on the front-side surface
of the low-loss dielectric substrate 21.
Fourth Embodiment
[0084] FIGS. 11A to 11C are a plan view, a bottom view, and a
sectional view taken along line B-B' in FIG. 11B, respectively, of
a structure of a resonator 50 according to a fourth embodiment.
[0085] Referring to FIGS. 11A to 11C, the resonator 50 is formed on
a low dielectric substrate 51 having a thickness of, for example,
0.5 .mu.m and composed of MgO or the like. Resonator areas 51A and
51B are formed on the low dielectric substrate 51 and spaced apart
by a middle area 51C.
[0086] An electrode pattern 52A having a thickness of, for example,
0.5 .mu.m and composed of, for example, a YBCO (Y--Ba--Cu--O)
high-temperature superconductor is formed on the bottom surface of
the low dielectric substrate 51 so as to cover the resonator area
51A. Furthermore, an electrode pattern 52B composed of a similar
high-temperature superconductor is formed on the bottom surface of
the low dielectric substrate 51 so as to cover the resonator area
51B.
[0087] Furthermore, the central portions of the electrode patterns
52A and 52B are connected with a connection electrode pattern 52C
therebetween in the middle area 51C on the bottom surface of the
low dielectric substrate 51. The connection electrode pattern 52C
is composed of a similar high-temperature superconductor and formed
having a width W and a length L. The electrode patterns 52A and 52B
and the connection electrode pattern 52C may be formed by forming
cutout portions 51a and 51b in the middle area 51C of a
high-temperature conductor film that uniformly covers the bottom
surface of the low dielectric substrate 51, the cutout portions 51a
and 51b being formed from sides of the high-temperature conductor
film toward a virtual center line connecting the centers of the
resonator areas 51A and 51B.
[0088] A disk-shaped electrode pattern 53A composed of the same
high-temperature superconductor as described above and having a
thickness of, for example, 0.5 .mu.m and a radius of, for example,
5.6 mm is formed on the top surface of the low dielectric substrate
51 in the resonator area 51A in such a manner that the disk-shaped
electrode pattern 53A and a circular area 52a hold the low
dielectric substrate 51 therebetween, the circular area 52a being a
part of the electrode pattern 52A. Similarly, a disk-shaped
electrode pattern 53B composed of the same high-temperature
superconductor as described above and having a thickness of, for
example, 0.5 .mu.m and a radius of, for example, 5.6 mm is formed
on the top surface of the low dielectric substrate 51 in the
resonator area 51B in such a manner that the disk-shaped electrode
pattern 53B and a circular area 52b hold the low dielectric
substrate 51 therebetween, the circular area 52b being a part of
the electrode pattern 52B.
[0089] A first feeder cutout portion 52c is formed in the electrode
pattern 52A on the bottom surface of the low dielectric substrate
51 in such a manner that the first feeder cutout portion 52c
reaches the circular area 52a from the periphery of the low
dielectric substrate 51 and exposes the bottom surface of the low
dielectric substrate 51. Similarly, a second feeder cutout portion
52d is formed in the electrode pattern 52B in such a manner that
the second feeder cutout portion 52d reaches the circular area 52b
from the periphery of the low dielectric substrate 51. The second
feeder cutout portion 52d also exposes the bottom surface of the
low dielectric substrate 51, and is formed parallel to the first
feeder cutout portion 52c in such a manner that the first feeder
cutout portion 52c and the second feeder cutout portion 52d face
each other.
[0090] Furthermore, an input-side conductive pattern 52e composed
of the same high-temperature superconductor as described above is
formed in the first feeder cutout portion 52c and on the exposed
bottom surface of the low dielectric substrate 51. Here, the
input-side conductive pattern 52e and the first feeder cutout
portion 52c form an input-side coplanar-type feeder line
(hereinafter referred to as an "input-side feeder line").
Similarly, an output-side conductive pattern 52f composed of the
same high-temperature superconductor as described above is formed
in the second feeder cutout portion 52d and on the exposed bottom
surface of the low dielectric substrate 51. Here, the output-side
conductive pattern 52f and the second feeder cutout portion 52d
form an output-side coplanar-type feeder line (hereinafter referred
to as an "output-side feeder line").
[0091] In the resonator 50 illustrated in FIGS. 11A to 11C,
resonators are formed in the resonator areas 51A and 51B. These
resonators are connected with the connection electrode pattern 52C
therebetween in the middle area 51C, and form a two-stage dual-mode
resonator.
[0092] FIG. 12 illustrates a reflection characteristic (S.sub.11
parameter) of the resonator 50 where the disk-shaped electrode
patterns 53A and 53B, each of which is an electrode pattern having
a radius of 5.6 mm, are arranged on the low dielectric substrate
51. The distance between the centers of the disk-shaped electrode
patterns 53A and 53B is 15.2 mm, the width W of the connection
electrode pattern 52C is set to 4 mm, and the length L of the
connection electrode pattern 52C is adjusted within the range of
8.7 mm to 13 mm.
[0093] Referring to FIG. 12, if the length L is short, that is, if
the electrode patterns 52A and 52B are arranged close to each other
with the cutout portions 51a and 51b therebetween, the resonance
frequencies f.sub.1, and f.sub.2 become close to each other and the
characteristics of the resonator 50 become similar to those of a
single-mode filter. In contrast, if the length L increases, the
resonance frequencies f.sub.1 and f.sub.2 become further away from
each other and the characteristics of the resonator 50 become
similar to those of a dual-mode filter. Moreover, if the length L
increases, the resonance frequencies f.sub.1 and f.sub.2 are
shifted and become lower.
[0094] FIG. 13 illustrates a relationship between an
inter-resonator coupling coefficient k.sub.dd and the length L. The
inter-resonator coupling coefficient k.sub.dd is obtained using the
resonance frequencies f.sub.1 and f.sub.2 in FIG. 12. Here, the
inter-resonator coupling coefficient k.sub.dd is expressed by the
expression
k.sub.dd=(f.sub.22-f.sub.12)/(f.sub.22+f.sub.12)(f.sub.2>f.sub.1).
[0095] Referring to FIG. 13, the inter-resonator coupling
coefficient k.sub.dd changes almost linearly as the length L
changes.
[0096] In the fourth embodiment, the input-side feeder line
including the first feeder cutout portion 52c and the input-side
conductive pattern 52e and the output-side feeder line including
the second feeder cutout portion 52d and the output-side conductive
pattern 52f are formed in the electrode patterns 52A and 52B so as
to reach the circular areas 52a and 52b, respectively, the
electrode patterns 52A and 52B being continuous on the back-side
surface of the low dielectric substrate 51. As a result, according
to the fourth embodiment, a capacitance obtained between the
input-side conductive pattern 52e and the electrode pattern 52A and
a capacitance obtained between the output-side conductive pattern
52f and the electrode pattern 52B increase, whereby strong coupling
may be achieved. That is, according to the fourth embodiment, loss
caused by using the resonator 50 or loss caused by using a filter
using the resonator 50 may be reduced more significantly than when
feeder lines are formed on the front-side surface of the low
dielectric substrate 51.
[0097] In the fourth embodiment, the low dielectric substrate 51 is
not limited to a MgO single crystal substrate and may alternatively
be a LaAIO.sub.3 single crystal substrate or a sapphire
substrate.
[0098] Furthermore, the electrode patterns 52A and 52B, the
connection electrode pattern 52C, the disk-shaped electrode
patterns 53A and 53B, and the input-side and output-side conductive
patterns 52e and 52f may alternatively be composed of, for example,
an R--Ba--Cu--O (RBCO) high-temperature superconductor film, that
is, a film composed of neodymium (Nd), samarium (Sm), gadolinium
(Gd), dysprosium (Dy), and holmium (Ho) instead of yttrium (Y) in
the YBCO high-temperature superconductor.
[0099] Furthermore, in the fourth embodiment, Ba--Sr--Ca--Cu--O
(BSCCO), Pb--Bi--Sr--Ca--Cu--O (PBSCCO), and
Cu--Ba.sub.p--Ca.sub.q--Cu.sub.r-Ox (CBCCO) (where 1.5<p<2.5,
2.5<q<3.5, 3.5<r<4.5) high-temperature superconductors
may alternatively be used.
[0100] Here, in the resonator 50 according to the fourth
embodiment, the electrode patterns 52A and 52B, the connection
electrode pattern 52C, the disk-shaped electrode patterns 53A and
53B, the input-side conductive pattern 52e, and the output-side
conductive pattern 52f may not be composed of a high-temperature
superconductor, and may alternatively be composed of a normal
conductor.
[0101] The resonator 50 illustrated in FIGS. 11A to 11C may also be
used as a filter.
Fifth Embodiment
[0102] FIG. 14 illustrates a superconducting filter 60 according to
the fifth embodiment.
[0103] Referring to FIG. 14, a superconducting filter 60 includes a
package container 61 that carries a wiring pattern (not shown)
formed as a microstrip line on the bottom portion of the package
container 61. The resonator 50 may be mounted on the bottom portion
of the package container 61 by a flip-chip method. Moreover, an
opening 61B corresponding to a center portion of the connection
electrode pattern 52C is formed in the bottom portion of the
package container 61.
[0104] Furthermore, a dielectric plate 62 composed of MgO,
sapphire, or the like is arranged above the resonator 50 in the
package container 61. The dielectric plate 62 is held by a cover
61L of the package container 61 using a screw 62B and the like in
such a manner that the dielectric plate 62 may be adjusted to be
closer to or further away from the resonator 50. The distance
between the dielectric plate 62 and the resonator 50 is in the
range of 0.01 mm to 10 mm.
[0105] Furthermore, in the superconducting filter 60, a rod 61C
corresponding to the ground slot 22B and having a screw shape is
formed in the opening 61B of the superconducting filter 60 in such
a manner that the rod 61C may be adjusted to be closer to or
further away from the connection electrode pattern 52C. The
distance h.sub.dd between the rod 61C and the connection electrode
pattern 52C is in the range of 0.0 mm to 0.7 mm.
[0106] FIGS. 15A to 15C illustrate a plan view, a bottom view, and
a sectional view taken along line C-C' in FIG. 15B, respectively,
of the resonator 50 in the package container 61. Here, in FIGS. 15A
to 15C, components the same as those indicated above will be
denoted by the same reference numerals and description thereof will
be omitted.
[0107] As illustrated in FIG. 15B, the rod 61C is provided in the
center of the connection electrode pattern 52C. In the fifth
embodiment, by providing the rod 61C in such a manner that the rod
61C may be adjusted to be closer to or further away from the
connection electrode pattern 52C, the inter-resonator coupling
coefficient k.sub.dd is controlled using the distance h.sub.dd,
whereby the passband characteristic of the superconducting filter
60 may be controlled.
[0108] FIG. 16 illustrates a reflection characteristic (S11) of the
superconducting filter 60 at a temperature of 70 K, and FIG. 17
illustrates the passband characteristic of the superconducting
filter 60 in cases where h.sub.dd=0.01 mm, h.sub.dd=0.06 mm,
h.sub.dd=0.11 mm, and h.sub.dd=0.61 mm. In FIG. 16, the length L is
set to 27 mm and the width W is set to, for example, 4 mm. In the
example in FIG. 16, a metal screw having a radius of 2 mm is used
as the rod 61C. Here, the rod 61C may be composed of a magnetic
material or a dielectric material such as MgO, LaAIO.sub.3,
TiO.sub.2, or the like.
[0109] As may be seen from FIGS. 16 and 17, the passband width of
the superconducting filter 60 decreases as the distance h.sub.dd
becomes larger and increases as the distance h.sub.dd becomes
smaller. Moreover, FIGS. 16 and 17 illustrate that if the distance
h.sub.dd is changed by the rod 61C, the center frequency of the
superconducting filter 60 changes If the distance h.sub.dd
decreases, the center frequency thereof is shifted and becomes
higher. If the distance h.sub.dd increases, the center frequency
thereof is shifted and becomes lower. However, such a shift
regarding the center frequency thereof may be compensated by
changing the distance between the dielectric plate 62 and the
resonator 50 using the screw 62B.
[0110] FIG. 18 illustrates a relationship between the
inter-resonator coupling coefficient k.sub.dd and the distance
h.sub.dd for the superconducting filter 60. The inter-resonator
coupling coefficient k.sub.dd is obtained at a temperature of 60 K
from the reflection characteristic illustrated in FIG. 16.
[0111] Referring to FIG. 18, if the distance h.sub.dd decreases,
the inter-resonator coupling coefficient k.sub.dd steeply
increases, whereby the passband width decreases. In contrast, if
the distance h.sub.slot increases, the effect of the ground slot
22B increases, whereby the passband width increases as illustrated
in FIGS. 8 and 9.
[0112] In the fifth embodiment, the input-side feeder line
including the first feeder cutout portion 52c and the input-side
conductive pattern 52e and the output-side feeder line including
the second feeder cutout portion 52d and the output-side conductive
pattern 52f are formed in the electrode patterns 52A and 52B so as
to reach the circular areas 52a and 52b, respectively. The
electrode patterns 52A and 52B are continuous on the back-side
surface of the low dielectric substrate 51. As a result, according
to the fifth embodiment, a capacitance obtained between the
input-side conductive pattern 52e and the electrode pattern 52A and
a capacitance obtained between the output-side conductive pattern
52f and the electrode pattern 52B increase, whereby strong coupling
may be achieved. That is, according to the fifth embodiment, loss
caused by using the superconducting filter 60 may be reduced more
significantly than when feeder lines are formed on the front-side
surface of the low dielectric substrate 51.
[0113] In the fifth embodiment, a steep passband characteristic may
be achieved by coupling two resonators as illustrated in FIG. 17.
Here, in the fifth embodiment, the number of resonators being
coupled to each other is not limited to two. Three or more
resonators may alternatively be coupled to each other.
[0114] In the superconducting filter 60, the dielectric plate 62
and the screws 62A and 62B may also be omitted.
Sixth Embodiment
[0115] FIGS. 19A to 19C are a plan view, a bottom view, and a
sectional view taken along line D-D' in FIG. 19B, respectively, of
a resonator 70 according to a sixth embodiment.
[0116] Referring to FIGS. 19A to 19C, the resonator 70 is formed on
a low-loss dielectric substrate 71 having a thickness of 0.5 mm and
composed of MgO or the like, for example. Resonator areas 71A and
71B are formed on the low-loss dielectric substrate 71 and spaced
apart by a middle area 71C.
[0117] An electrode pattern 72A having a thickness of, for example,
0.5 .mu.m and composed of, for example, a YBCO (Y--Ba--Cu--O)
high-temperature superconductor is formed on the bottom surface of
the low-loss dielectric substrate 71 so as to cover the resonator
area 71A. Furthermore, an electrode pattern 72B composed of a
similar high-temperature superconductor is formed on the bottom
surface of the low-loss dielectric substrate 71 so as to cover the
resonator area 71B.
[0118] Furthermore, the central portions of the electrode patterns
72A and 72B are connected to each other in the middle area 71C on
the bottom surface of the low-loss dielectric substrate 71. A
connection electrode pattern 72C composed of a similar
high-temperature superconductor is formed having a width W and a
length L. The electrode patterns 72A and 72B and the connection
electrode pattern 72C are formed by forming cutout portions 71a and
71b in the middle area 71C on a high-temperature conductor film
that uniformly covers the bottom surface of the low-loss dielectric
substrate 71. The cutout portions 71a and 71b extend from sides of
the high-temperature conductor film toward a virtual center line
connecting the resonator areas 71A and 71B.
[0119] A disk-shaped electrode pattern 73A composed of the same
high-temperature superconductor as described above and having a
thickness of 0.5 .mu.m and a radius of 5.6 mm is formed in the
resonator area 71A on the top surface of the low-loss dielectric
substrate 71 in such a manner that the disk-shaped electrode
pattern 73A and a circular area 72a hold the low-loss dielectric
substrate 71 therebetween. The circular area 72a is a part of the
electrode pattern 72A. Similarly, a disk-shaped electrode pattern
73B composed of the same high-temperature superconductor as
described above and having, for example, a thickness of 0.5 .mu.m
and a radius of 5.6 mm is formed in the resonator area 71B on the
top surface of the low-loss dielectric substrate 71 in such a
manner that the disk-shaped electrode pattern 73B and a circular
area 72b hold the low-loss dielectric substrate 71 therebetween.
The circular area 72b is a part of the electrode pattern 72B.
[0120] A first feeder cutout portion 72c is formed in the electrode
pattern 72A on the bottom surface of the low-loss dielectric
substrate 71 in such a manner that the first feeder cutout portion
72c reaches the circular area 72a from the periphery of the
low-loss dielectric substrate 71 and exposes the bottom surface of
the low-loss dielectric substrate 71. Similarly, a second feeder
cutout portion 72d is formed in the electrode pattern 72B in such a
manner that the second feeder cutout portion 72d reaches the
circular area 72b from the periphery of the low-loss dielectric
substrate 71. The second feeder cutout portion 72d also exposes the
bottom surface of the low-loss dielectric substrate 71. The second
feeder cutout portion 72d is formed parallel to the first feeder
cutout portion 72c and perpendicular to an imaginary line that
connects the centers of the circular areas 72a and 72b.
[0121] In the electrode pattern 72A, a circular ground slot 72AG
similar to the ground slot 22B illustrated in FIG. 2B is formed in
a part of the circular area 72a at a position away from the center
of the circular area 72a. Similarly, in the electrode pattern 72B,
a circular ground slot 72BG similar to the circular ground slot
72AG is formed in part of the circular area 72b at a position away
from the center of the circular area 72b.
[0122] Furthermore, an input-side conductive pattern 72e composed
of the same high-temperature superconductor as described above is
formed in the first feeder cutout portion 72c and on the exposed
bottom surface of the low-loss dielectric substrate 71. Here, the
input-side conductive pattern 72e and the first feeder cutout
portion 72c form an input-side coplanar-type feeder line
(hereinafter referred to as an "input-side feeder line").
Similarly, an output-side conductive pattern 72f composed of the
same high-temperature superconductor as described above is formed
in the second feeder cutout portion 72d and on the exposed bottom
surface of the low-loss dielectric substrate 71. Here, the
output-side conductive pattern 72f and the second feeder cutout
portion 72d form an output-side coplanar-type feeder line
(hereinafter referred to as an "output-side feeder line").
[0123] In the resonator 70 illustrated in FIGS. 19A to 19C,
resonators are formed in the resonator areas 71A and 71B. These
resonators are connected to each other via the connection electrode
pattern 72C in the middle area 71C, and form a two-stage dual-mode
resonator.
[0124] FIG. 20 illustrates a reflection characteristic (S.sub.11
parameter) and a transmission characteristic (S.sub.21 parameter)
of the resonator 70 in a case where the disk-shaped electrode
patterns 73A and 73B, each of which is an electrode pattern having
a radius of 5.6 mm, are arranged on the low-loss dielectric
substrate 71. The distance between the centers of the disk-shaped
electrode patterns 73A and 73B may be, for example, 15.2 mm, the
width W of the connection electrode pattern 72C is set to 4 mm, the
length L of the connection electrode pattern 72C is set to, for
example, 8.7 mm, and the radii of the circular ground slots 72AG
and 72BG are set to, for example, 0.97 mm.
[0125] As may be seen from FIG. 20, as a transmission
characteristic, resonance frequencies f.sub.1, f.sub.2, f.sub.3,
and f.sub.4 are obtained for the two-stage dual mode resonator,
that is, a four-stage resonator, and a passband is formed between
the resonance frequencies f.sub.2 and f.sub.3. In an example in
FIG. 20, a bandwidth of -3 dB indicates 87 MHz, and steepness
indicates -30 dB/(26 to 29 MHz).
[0126] In the sixth embodiment, the input-side feeder line
including the first feeder cutout portion 72c and the input-side
conductive pattern 72e and the output-side feeder line including
the second feeder cutout portion 72d and the output-side conductive
pattern 72f are formed in the electrode patterns 72A and 72B so as
to reach the circular areas 72a and 72b, respectively. The
electrode patterns 72A and 72B are continuous on the back-side
surface of the low-loss dielectric substrate 71. As a result,
according to the sixth embodiment, a capacitance obtained between
the input-side conductive pattern 72e and the electrode pattern 72A
and a capacitance obtained between the output-side conductive
pattern 72f and the electrode pattern 72B increase, whereby strong
coupling may be achieved. That is, according to the sixth
embodiment, loss caused by using the resonator 70 or loss caused by
a filter using the resonator 70 may be more significantly reduced
than when feeder lines are formed on the front-side surface of the
low-loss dielectric substrate 71.
[0127] Here, in the sixth embodiment, the low-loss dielectric
substrate 71 is not limited to a MgO single crystal substrate and
may alternatively be a LaAIO.sub.3 single crystal substrate or a
sapphire substrate.
[0128] Furthermore, the electrode patterns 72A and 72B, the
connection electrode pattern 72C, the disk-shaped electrode
patterns 73A and 73B, and the input-side and output-side conductive
patterns 72e and 72f may not be composed of the YBCO
high-temperature superconductor and may alternatively be composed
of, for example, R--Ba--Cu--O (RBCO) high-temperature
superconductor film, that is, a film composed of neodymium (Nd),
samarium (Sm), gadolinium (Gd), dysprosium (Dy), and holmium (Ho)
instead of yttrium (Y) in the YBCO high-temperature
superconductor.
[0129] Furthermore, in the sixth embodiment, Ba--Sr--Ca--Cu--O
(BSCCO), Pb--Bi--Sr--Ca--Cu--O (PBSCCO), and
Cu--Ba.sub.p--Ca.sub.q--Cu.sub.r-Ox (CBCCO) (where 1.5<p<2.5,
2.5<q<3.5, 3.5<r<4.5) high-temperature superconductors
may alternatively be used.
[0130] In the sixth embodiment, the intensity of an electric field
may be reduced or prevented from being high and a problem of an
electrode layer 72 losing superconductivity because of an intense
electric field may be prevented by forming the circular ground
slots 72AG and 72BG in a circular shape.
[0131] In the resonator 70 according to the sixth embodiment, the
electrode patterns 72A and 72B, the connection electrode pattern
72C, the disk-shaped electrode patterns 73A and 73B, the input-side
conductive pattern 72e, and the output-side conductive pattern 72f
may not be composed of a high-temperature superconductor, and may
alternatively be composed of a normal conductor.
[0132] In the sixth embodiment, a steep passband characteristic as
illustrated in FIG. 17 may be achieved by coupling two dual-mode
resonators. Here, in the sixth embodiment, the number of dual-mode
resonators being coupled to each other is not limited to two. Three
or more dual-mode resonators may alternatively be coupled to each
other.
[0133] The resonator 70 illustrated in FIGS. 19A to 19C may also be
used as a filter.
Seventh Embodiment
[0134] FIG. 21 illustrates a superconducting filter 80 according to
the seventh embodiment.
[0135] Referring to FIG. 21, the superconducting filter 80 includes
a package container 81 that carries a wiring pattern (not shown)
formed as a microstrip line on the bottom portion of the package
container 81, and the resonator 70 is mounted on the bottom portion
of the package container 81 by a flip-chip method. Moreover,
openings 81A and 81B corresponding to the circular ground slots
72AG and 72BG and an opening 81C corresponding to a center portion
of the connection electrode pattern 72C are formed on the bottom
portion of the package container 81.
[0136] Furthermore, a dielectric plate 82 composed of MgO,
sapphire, or the like is arranged above the resonator 70 in the
package container 81. The dielectric plate 82 is held by a cover
81L of the package container 81 using screws 82A and 82B and the
like in such a manner that the dielectric plate 82 may be adjusted
to be closer to or further away from the resonator 70. The distance
between the dielectric plate 82 and the resonator 70 may be
adjusted to be in the range of 0.01 mm to 10 mm.
[0137] Furthermore, rods 81D and 81E corresponding to the circular
ground slots 72AG and 72BG and each having a screw shape are formed
in the openings 81A and 81B of the superconducting filter 80,
respectively, in such a manner that the rods 81D and 81E may be
adjusted to be closer to or further away from the low-loss
dielectric substrate 71. The distance h.sub.slot between the rod
81D and the low-loss dielectric substrate 71 and the distance
h.sub.slot between the rod 81E and the low-loss dielectric
substrate 71 may be in the range of 0.01 mm to 1 mm. Moreover, the
opening 81C corresponding to the center portion of the connection
electrode pattern 72C is formed on the bottom portion of the
package container 81, and a rod 81F is held in the opening 81C in
such a manner that the rod 81F may be adjusted to be closer to or
further away from the connection electrode pattern 72C. The
distance h.sub.dd between the rod 81F and the connection electrode
pattern 72C may be in the range of 0.0 mm to 0.7 mm. Here, the rods
81D to 81F may be composed of a magnetic material or a dielectric
material such as MgO, LaAIO.sub.3, TiO.sub.2, or the like.
[0138] FIGS. 22A to 22C are a plan view, a bottom view, and a
sectional view taken along line E-E' in FIG. 22B, respectively, of
the resonator 70 in the package container 81. In FIGS. 22A to 22C,
components the same as those indicated above will be denoted by the
same reference numerals and description thereof will be omitted.
The sectional view in FIG. 21 is actually a sectional view taken
along line E-E'.
[0139] As illustrated in FIG. 22B, similarly to the rod 61C
illustrated in FIG. 15B, the rod 81F is provided in the center of
the connection electrode pattern 72C. In the seventh embodiment, by
providing the rod 81F in such a manner that the rod 81F may be
adjusted to be closer to or further away from the connection
electrode pattern 72C, the inter-resonator coupling coefficient
k.sub.dd is controlled using the distance h.sub.dd, whereby the
passband characteristic of the superconducting filter 80 is
controlled. Moreover, by providing the rods 81D and 81E in such a
manner that the rods 81D and 81E may be adjusted to be closer to or
further away from the low-loss dielectric substrate 71, the
passband characteristic of the superconducting filter 80 may be
controlled using the inter-resonator coupling coefficient
k.sub.dd.
[0140] In the superconducting filter 80, the dielectric plate 82
and the screws 82A and 82B may be omitted.
[0141] In the seventh embodiment, the input-side feeder line
including the first feeder cutout portion 72c and the input-side
conductive pattern 72e and the output-side feeder line including
the second feeder cutout portion 72d and the output-side conductive
pattern 72f are formed in the electrode patterns 72A and 72B so as
to reach the circular areas 72a and 72b, respectively. The
electrode patterns 72A and 72B are continuous on the back-side
surface of the low-loss dielectric substrate 71. As a result,
according to the seventh embodiment, a capacitance obtained between
the input-side conductive pattern 72e and the electrode pattern 72A
and a capacitance obtained between the output-side conductive
pattern 72f and the electrode pattern 72B increase, whereby strong
coupling may be achieved. That is, according to the seventh
embodiment, the efficiency of the superconducting filter 80 using
the resonator 70 may be improved more significantly than when
feeder lines are formed on the front-side surface of the low-loss
dielectric substrate 71.
Eighth Embodiment
[0142] FIG. 23 illustrates a schematic structure of a GHz-band
transmitter-receiver 90 using a superconducting filter according to
any one of the first to seventh embodiments.
[0143] Referring to FIG. 23, the GHz-band transmitter-receiver 90
includes a baseband unit 91 that includes an integrated circuit
device. The baseband unit 91 generates a transmission signal, and
the transmission signal is modulated by a modulator 92A and the
modulated signal is converted into a microwave signal by an
up-converter 93A. After the microwave signal is amplified by a
power amplifier 94A, the amplified signal is supplied to an antenna
96 via a superconducting filter 95A according to any one of the
first to seventh embodiments.
[0144] Moreover, the signal supplied to the antenna 96 is supplied
to a low-noise amplifier 94B through a superconducting filter 95B.
After the signal is amplified by the low-noise amplifier 94B, the
amplified signal is converted into a high-frequency signal by a
down-converter 93B. After the high-frequency signal is demodulated
by a demodulator 92B, the demodulated signal is supplied to the
baseband unit 91. Furthermore, a cryostat 97 is provided for
cooling the superconducting filter 95A.
[0145] In the GHz-band transmitter-receiver 90 illustrated in FIG.
23, loss is small, operation may be efficiently performed, and
power consumption may be reduced because the superconducting filter
95A has a superconducting electrode layer. Moreover, by using a
high-temperature superconductor composed of an oxide as the
superconducting electrode layer, superconductivity is maintained
even in a liquid nitrogen temperature range of 60 to 80 K, whereby
the power consumption of the cryostat 97 may be reduced.
[0146] The GHz-band transmitter-receiver 90 may be applied to, for
example, base stations for mobile communication.
[0147] All examples and conditional language recited herein are
intended for pedagogical purposes to aid the reader in
understanding the invention and the concepts contributed by the
inventor to furthering the art, and are to be construed as being
without limitation to such specifically recited examples and
conditions, nor does the organization of such examples in the
specification relate to a showing of the superiority and
inferiority of the invention. Although the embodiments of the
present inventions have been described in detail, it should be
understood that the various changes, substitutions, and alterations
could be made hereto without departing from the spirit and scope of
the invention.
* * * * *